There are numerous different electrically-energized utilization systems that should have an A.C. input within a given normal voltage range. One example is an A.C. energized air conditioner; if the A.C. line energizing the air conditioner falls below a given threshold voltage level, whether permanently or for a substantial period of time, the air conditioner may overheat and may suffer permanent damage. Another example is a telephone or other telecommunication system or a battery charger that relies upon an A.C. input voltage in a given normal range. When the input voltage exceeds the upper limit of that range for any substantial period of time, the system may be severely damaged or even virtually destroyed. Other utilization systems may react adversely to inputs either above or below their normal input voltage range.
Compensation circuits have been proposed for both over-voltage and under-voltage A.C. power line conditions. For the most part, known voltage compensation devices have been relatively large and expensive. Indeed, the cost of an effective voltage compensation device may be comparable to the cost of the utilization apparatus that it protects.